A silicon monocrystal has been widely used as a semiconductor material. According to a typical method of manufacturing a silicon monocrystal, a silicon-polycrystal material is recrystallized to be grown as monocrystal ingot(s). The obtained silicon monocrystal is sliced into wafers of a predetermined thickness.
With respect to growing a silicon monocrystal, several technologies are under development so as to improve the quality thereof.
In principle, a crystal grown by a floating zone (FZ) method can be made to have resistivity distribution that is uniform in a longitudinal direction of the grown crystal by using a gas doping method on a polycrystalline material having high resistivity.
Meanwhile, in order to reduce manufacturing cost, there has been also a need for a grown crystal having a large diameter in a field of, for instance, a discrete device in recent years. It is preferable to use a silicon-polycrystal material having a diameter of 140 mm or more for manufacturing a grown crystal having a large diameter, particularly a diameter of 150 mm or more.
However, when such a silicon-polycrystal material having a large diameter is used, the manufacturing cost is contrarily increased because a price of such a raw material is set high due to an yield problem in manufacturing the raw material itself.
One solution of such a problem may be to use a P-type or N-type silicon crystal having been pulled up by CZochralski method as the raw material for forming a crystal by FZ method.
For instance, in order to manufacture a high-quality P-type or N-type silicon monocrystal of low resistivity, Patent Document 1 proposes a technology to recrystallize a silicon-material bar having resistivity of 0.1 Ω·cm (manufactured by CZ method) by FZ method.
Additionally, in order to manufacture a high-quality P-type or N-type silicon monocrystal of high resistivity, Patent Document 2 proposes a technology to recrystallize a silicon-material bar having resistivity of 1000 Ω·cm (manufactured by CZ method) by FZ method.    [Patent Document 1] JP-A-2005-281076    [Patent Document 2] JP-A-2005-306653